[Info-vax] Poulson info from Dave Cantor

[H Vlems]

On 18 nov, 19:32, billg... at cs.uofs.edu (Bill Gunshannon) wrote:
> In article <ic3qtf$9a... at news.eternal-september.org>,
>         glen herrmannsfeldt <g... at ugcs.caltech.edu> writes:
>
>
>
>
>
> > John Reagan <johnrrea... at earthlink.net> wrote:
> > (snip)
>
> >> They are not MY compilers.   There are email addresses in the PPT slides
> >> that Tim posted.  Ask them.
>
> >>> The author writes: "Itanium relies on compilers to aggressively
> >>> schedule instructions for parallel execution into bundles."
> >>> What does "...aggressivively schedule..." mean in terms of compiler
> >>> design ?
>
> > I would ask in comp.compilers.  It is moderated, but that is where
> > the people that really know compilers are.
>
> >> To get good execution on Itanium, a compiler needs to analyze the code to
> >> figure out which things can be done in parallel or not.  It is then upto the
> >> compiler to organize those in bundles according to the bundle type (which
> >> only provides certain permutations).
>
> >> I suspect that code that runs today will run just fine in the future, but
> >> assumes that code that "runs" today isn't technically illegal.  Remember the
> >> situation with certain operations inside Alpha load-locked/store-conditional
> >> sequences?  They "worked" in early Alphas, but newer Alphas caught them.  We
> >> fixed the compilers but there was the worry that old .OBJs and .EXEs still
> >> are out there.  Thats where the CHECK_SRM tool (or whatever its name is)
> >> came from.  It lets you scan existing .EXEs to see if they have the bad
> >> seqeunces.
>
> > That tends to be a problem with RISC, and even worse with VLIW.
>
> > Note that IBM's z/OS running on z/Architecture machines currently
> > in production will run object and executables written over 40 years
> > ago for OS/360 on S/360 hardware.  There are incompatible changes
> > in privileged instructions, but problem state code runs just fine.  
>
> It is my understanding that the same is true of Unisys.
>
> bill
>
> --
> Bill Gunshannon          |  de-moc-ra-cy (di mok' ra see) n.  Three wolves
> billg... at cs.scranton.edu |  and a sheep voting on what's for dinner.
> University of Scranton   |
> Scranton, Pennsylvania   |         #include <std.disclaimer.h>  - Tekst uit oorspronkelijk bericht niet weergeven -
>
> - Tekst uit oorspronkelijk bericht weergeven -

I know that is true for what used to be the Burroughs side of Unisys.
B6700/B7700 code will run unmodified
on a modern (though emulated) system. Compiling old code is not
trivial though. Last year I compiled an old
program and had to remove and modify several file attributes because
the old ones were no longer supported.
Hans